sound deadening, engine compartment pad Options

[dlindzey]

there are at least two different versions on the usual parts sites-
aase $200
pelican $125
AA $200

any practical experience or obvious best choice in taking care of this need?

[Dion]

I’m using this. Can’t report on decibel reduction as I’m not up and running yet.
It is well made though. Lightweight, easy install.

RIX 914 parts https://www.rix914parts.com/store/p29/914_F...uction_Mat.html

[PanelBilly]

Just make sure it’s secure and can’t get sucked into the engine.

[bbrock]

Hey @Dion , I look forward to hearing how you like that pad. I may go that route if I'm not satisfied with the pad I installed. To @PanelBilly 's comment, it looks like you are missing the plastic buttons needed to secure the pad to the firewall. They are NAPA part number 665-3116 (IMG:style_emoticons/default/beerchug.gif)

[Literati914]

Do you guys not worry about moisture getting trapped by these, even the stock ones?

Seems a press-on/sticky type would be better in that regard, if there's no concern for stock appearance.. but still, I'd be concerned. Fixing rust sucks.


.

[Chris914n6]

I'd consider the 914rubber pad as it seems to be close as possible to the original using modern materials.

Only $135 + shipping

https://914rubber.com/foam-damping-mat-engine-bay-firewall-1

[Dion]

Brent @bbrock , well super efficient Dion here welded all those holes closed! I lost my way a bit when closing my 5 point harness holes up.
So those got caught in the mix :-/ Will be addressing this later. Thanks for the heads up though:-)

[Mark Henry]

Do you guys not worry about moisture getting trapped by these, even the stock ones?

Seems a press-on/sticky type would be better in that regard, if there's no concern for stock appearance.. but still, I'd be concerned. Fixing rust sucks.


.

No, my teen is always garaged and I try not to drive in the rain.

Look at what stock is, look at the whole thing. hard rubber outer with the fiber (horsehair?), then the steel but your not done. The other side you have the fitted rubber/tar sheet glued to the firewall and the whole back pad. You take away any part of that sandwich and it will add noise.

To me just some dynamat or whatever is crap, I'd look to replicate that sandwich with modern materials.
It's going to have some weight, if it's a street car you have to live with that fact.

[bbrock]

Do you guys not worry about moisture getting trapped by these, even the stock ones?

Seems a press-on/sticky type would be better in that regard, if there's no concern for stock appearance.. but still, I'd be concerned. Fixing rust sucks.


.

No, my teen is always garaged and I try not to drive in the rain.

Look at what stock is, look at the whole thing. hard rubber outer with the fiber (horsehair?), then the steel but your not done. The other side you have the fitted rubber/tar sheet glued to the firewall and the whole back pad. You take away any part of that sandwich and it will add noise.

To me just some dynamat or whatever is crap, I'd look to replicate that sandwich with modern materials.
It's going to have some weight, if it's a street car you have to live with that fact.

(IMG:style_emoticons/default/agree.gif) 200%

[Literati914]

..
Look at what stock is, look at the whole thing. hard rubber outer with the fiber (horsehair?), then the steel but your not done. The other side you have the fitted rubber/tar sheet glued to the firewall and the whole back pad. You take away any part of that sandwich and it will add noise.

To me just some dynamat or whatever is crap, I'd look to replicate that sandwich with modern materials.
It's going to have some weight, if it's a street car you have to live with that fact.

I've had two 914s with stock engine side pads.. both just seemed like loose-fitting, worn out rubber sheeting to me.. I didn't notice any layers to them. Maybe those were something other than stock (IMG:style_emoticons/default/confused24.gif) , IDK.. then the other side (you mean the back-pad side?), neither cars had anything between the back pad and fire wall. I'm sure layering would be effective at noise tho. Maybe dynamat on both sides?


.

[bbrock]

..
Look at what stock is, look at the whole thing. hard rubber outer with the fiber (horsehair?), then the steel but your not done. The other side you have the fitted rubber/tar sheet glued to the firewall and the whole back pad. You take away any part of that sandwich and it will add noise.

To me just some dynamat or whatever is crap, I'd look to replicate that sandwich with modern materials.
It's going to have some weight, if it's a street car you have to live with that fact.

I've had two 914s with stock engine side pads.. both just seemed like loose-fitting, worn out rubber sheeting to me.. I didn't notice any layers to them. Maybe those were something other than stock (IMG:style_emoticons/default/confused24.gif) , IDK.. then the other side (you mean the back-pad side?), neither cars had anything between the back pad and fire wall. I'm sure layering would be effective at noise tho. Maybe dynamat on both sides?
.

Dynamat is good for quieting the resonant booming/drumming sound of large panels like floors and doors, it is not good at stopping the airborne drone of an engine. That's where those layers come in. Different sound deadening materials are needed to address different noise sources. And even the constrained layer (e.g. Dynamat) manufacturers recommend adding a dense layer of padding under the carpet.

[Mark Henry]

I've had two 914s with stock engine side pads.. both just seemed like loose-fitting, worn out rubber sheeting to me.. I didn't notice any layers to them. Maybe those were something other than stock (IMG:style_emoticons/default/confused24.gif) , IDK.. then the other side (you mean the back-pad side?), neither cars had anything between the back pad and fire wall. I'm sure layering would be effective at noise tho. Maybe dynamat on both sides?


.

Then you have tar pad, steel, tar pad...IMHO that's wrong.
You need a tar pad, steel, foam pad and then rubber pad. Maybe use some heavy rubber roof liner, but I don't know if that material is fireproof enough.

The dynamat will work as part of the sandwich, as does the stock back pad. The engine bay has to have something that replicates the stock pad. You could try stripping out the horse hair for the stock pad and glueing in something like a closed cell foam.

I'm no sound engineer but anecdotally I know it's the sum of the layers that reduces noise, not any one layer. BTW also make sure the glass is sealed.

My /6 conversion I used the stock backpad, but I reglued it and made sure the big plastic washers were secure. I now notice that the mid-seam each side is starting to loosen so I plan to secure them as well, maybe with a strip of 1/8" alunimum.

My weber carb /6 is not noisy at cruise, you can easily have a conversation without shouting and there's no drone. But the engine is loud, so I know the sound deading is for sure working.

[davep]

Just think what it was like without the engine side sound deadening. I was in a 914/6 conversion one day then the pad got sucked against the fan. Fortunately no permanent damage was done, but I have remembered that experience for 40 years.

[Chris914n6]

On modern cars the sound absorbers are the under hood pad and strategically placed foam under the engine cover. The firewall sometimes has a heat block of sheet aluminum.

The quiet cabin comes from all the stuff inside: vibration dampeners, molded foam under the carpet, foam pads behind the dash, plastic trim and in doors, and soft surfaces. Plus being tightly sealed.

What was the pad on the 993?

[Morph914]

I used the pad from 914 Rubber and am very happy with it. Looks a lot like the original but quite a bit lighter. As far as sound control, I cannot comment as I have not run the car yet.



As far as the interior side, I put some Noico sound deadened down under the original mat, this should be better than what the mat alone provided.

[Montreal914]

Looks like a very nice interior rebuild Morph914 (IMG:style_emoticons/default/smile.gif)

Small OT: Curious about the cross member vinyl covering, did you glue it in place? looks to be conforming very nicely to the metal.

[Literati914]

Neither of my current project cars (both '72 models) have the small rectangular tabs at the top, on the engine side that traps the sound deadener.. they don't look to have been broken off either - is that a years specific thing?


PS - Morph's 914rubber sound deadener look great. Heck I may have to change my mind on these things.

[Montreal914]

If I recall the tabs appeared in MY73 for the engine bay sound deadening. Coinciding with the arrival of the 2 liter engine.

[Root_Werks]

A few have already mentioned it, if you install ensure it's secure. Especially on a six. The padding gets pretty close to the fan.

My six conversion doesn't have a pad, but I would like one.

[bkrantz]

..
Look at what stock is, look at the whole thing. hard rubber outer with the fiber (horsehair?), then the steel but your not done. The other side you have the fitted rubber/tar sheet glued to the firewall and the whole back pad. You take away any part of that sandwich and it will add noise.

To me just some dynamat or whatever is crap, I'd look to replicate that sandwich with modern materials.
It's going to have some weight, if it's a street car you have to live with that fact.

I've had two 914s with stock engine side pads.. both just seemed like loose-fitting, worn out rubber sheeting to me.. I didn't notice any layers to them. Maybe those were something other than stock (IMG:style_emoticons/default/confused24.gif) , IDK.. then the other side (you mean the back-pad side?), neither cars had anything between the back pad and fire wall. I'm sure layering would be effective at noise tho. Maybe dynamat on both sides?
.

Dynamat is good for quieting the resonant booming/drumming sound of large panels like floors and doors, it is not good at stopping the airborne drone of an engine. That's where those layers come in. Different sound deadening materials are needed to address different noise sources. And even the constrained layer (e.g. Dynamat) manufacturers recommend adding a dense layer of padding under the carpet.

Right now, I plan to have Dynamat, acoustic foam, and then carpet on the inside. Once I hear it run, I will consider if and what to put on the engine side.